The invention relates to a housing for a gas turbine. The invention further relates to a gas turbine as well as a process for operating a gas turbine.
Gas turbines with variably adjustable guide blades are known from the prior art. Typically, guide blades are rotatably housed in a housing of the gas turbine for adjustment, in which the blade leaves of the guide blades are arranged in a flow channel of the housing of the gas turbine. Variably adjustable guide blades in a gas turbine particularly enable the adjustment of the absorption capacity of a turbine as well as the selective adaptation of the flow to downstream rotors. A gas turbine can thereby be particularly well-adjusted for various operating points, which reduces fuel consumption.
U.S. Pat. No. 2,919,890 discloses, in addition to variably adjustable guide blades, a housing for a gas turbine comprising a plurality of wall elements, which are housed so as to move in the housing and are subjected to targeted force in a direction of the flow channel via a spring. Thereby, various thermal expansions of the various housing elements and the guide blades can be compensated for.
However, what is disadvantageous with the known housings is that a sufficiently large gap must always be provided between the blade leaves of the guide blades and the adjacent wall element in order to also ensure the adjustability of the guide blades, in addition to the tolerance compensation, during operation of the assigned gas turbine. This gap, which is also characterized as the flag gap, leads to so-called throttle losses. These throttle losses reduce the level of efficiency and cause an increased fuel consumption in the gas turbine. In the worst-case scenario, this increased fuel consumption can overcompensate for the reduction in fuel consumption that can be achieved from the variable adjustment and make the adjustability of the guide blade thus unnecessary.
The object of the present invention is to obtain a housing for a gas turbine, which, on one hand, enables reliable guide blade adjustment and, on the other hand, enables improved efficiency of an assigned gas turbine. Another object of the invention is to provide a gas turbine with such a housing as well as a process for operating a turbine having such a housing.
A first aspect of the invention relates to a housing for a gas turbine. In order to enable reliable guide blade adjustment, on one hand, and an improved level of efficiency of an assigned gas turbine, on the other hand, a provision according to the invention is that the wall element be movable between a sealing setting, in which the wall element makes contact at least at a partial area of a side of a blade leaf of the guide blade facing toward the wall element, and an open setting, in which the blade leaf and the wall element are spaced apart from one another. In other words, a provision according to the invention is that the wall element be movable into an open setting, on one hand, in which a sufficiently large gap is formed between the wall element and the blade leaf of the guide blade in order to adjust the guide blade. On the other hand, a provision is that the wall element be movable into a sealing setting, in which the side of the blade leaf of the guide blade facing toward the wall element makes contact with at least part of the wall element. In the sealing setting, the flag gap is thus partially, predominantly, or completely closed, whereby corresponding throttle losses are greatly reduced or completely prevented during operation of the assigned gas turbine. Thus, the level of efficiency of the assigned gas turbine is improved, on one hand, while the adjustability of the guide blade is further assured, on the other hand. Contrary to a wearing seal, which could be realized, for example, by means of brushes, slides, or the like, wear furthermore does not occur on the adjustable blade leaf or on the wall element. Therefore, the housing according to the invention is particularly low-maintenance. In addition, no structural or aerodynamic modification of the guide blade is necessary, which could influence its service life or the effect on the gas flow disadvantageously. The adjustable guide blade in this case can essentially be formed as a turbine guide blade or as a compressor guide blade. Furthermore, essentially multiple adjustable guide blades can be provided, which are arranged next to one another in the circumferential direction of the housing with respect to a guide blade ring. The adjustable guide blades in this case may also be combined into guide blade segments. Similarly, multiple adjustable wall elements, which may also be characterized as annular area segments, may be arranged next to one another in the circumferential direction of the housing into a complete ring radially adjacent to the flow channel toward the exterior.
In another advantageous embodiment of the invention, a provision is that the wall element be subjected to fluid under pressure in order to move between the open setting and the sealing setting. For this purpose, the wall element may border, for example, a hollow space subjected to pressure, together with further housing elements. Fluids under pressure can be created for gas turbines without special effort. For example, compressed air in the form of so-called bleed air from a compressor stage of the gas turbine can be drawn off as fluid. The drawing off of bleed air or compressed air from the compressor of gas turbines is known and already being provided with many aircraft engines. With the use of a gas turbine in an aircraft engine there is additionally a sufficient amount of air pressure in the form of dynamic pressure, starting at a certain speed of an airplane, helicopter, or the like. Accordingly, the wall element can be subjected to pressure in a particularly simple and particularly economical manner. The number of moving parts is especially low in this case, especially in contrast to the use of an actuator, for example. Thus, the housing and therefore also a gas turbine equipped with the housing can be particularly formed in a low-maintenance and easy manner. This is of particularly great significance in airplane construction. Alternatively, when using a hydraulic actuator, the hydraulic system typically already present on airplanes, for example, can be used.
It is particularly advantageous for the invention when the housing includes a pressure supply line for supplying the fluid under pressure and a pressure relief line for discharging the fluid under pressure. The pressure on the wall element can be increased accordingly by supplying the fluid under pressure via the pressure supply line, while the pressure on the wall element can be correspondingly reduced by draining the fluid via the pressure relief line. The pressure supply line can form, for example, a channel to one of the compressor stages of the gas turbine. Alternatively, the pressure supply line can form a channel to the environment of the gas turbine so that the wall element can be subjected to the ambient pressure. Alternatively, it is also possible, for example, for the pressure supply line to be a passageway opening in an aircraft engine, by which the wall element can be subjected to dynamic pressure generated by the movement of the airplane, helicopter, or the like. In an advantageous manner, increased pressure causes a movement of the wall element into the closed setting, so that the flag gap is by default at least for the most part closed during operation of an assigned gas turbine. The movement of the wall element into the open setting is effected in this case by a relative pressure reduction or by a draining off of the fluid under pressure. The pressure relief line can be routed, for example, into the environment. This movement can be supported by a pressure in the flow channel, which acts upon the wall element. However, it is also possible to reverse this effective principle, which means that a sufficient pressure increase effects a movement of the wall element into the open setting, while a pressure reduction effects a movement of the wall element into the sealing setting. Thus, the movement of the wall element between the sealing setting and the open setting can be effected with particularly technically simple and economical means.
In a further advantageous embodiment of the invention, a provision is that the pressure supply line and/or the pressure relief line include a valve, by which the pressure on the wall element can be controlled and/or regulated. This enables a particularly precise control and/or regulating of the movement of the wall element between the sealing setting and the open setting. The control or regulation of the valve can take place as a function of the operating parameters of the gas turbine. To this end, the valve can be coupled, for example, to a control and/or regulating mechanism of the gas turbine.
In a particularly advantageous embodiment of the invention, a provision is that a drain-off channel of the pressure relief line have a larger cross-section than an access channel of the pressure supply line. The larger cross-section of the drain-off channel enables a particularly quick pressure reduction and thus a particularly quick movement of the wall element between the open and the sealing setting. In addition, this hereby makes it possible to use only one valve on the pressure relief line and thus to keep the number of parts as well as the weight of the housing as low as possible. When the valve is open, more fluid can be discharged then can be simultaneously supplied via the pressure supply line due to the larger cross-section of the drain-off channel, whereby quick pressure reduction is achieved.
Furthermore, it has been shown to be advantageous when the wall element is retained on a housing element on one side by a bearing. The bearing reduces at least one of the degrees of freedom of the moving wall element. The wall element can be moved relative with respect to the adjacent housing element via the bearing and can be pivoted or bent, for example, between the sealing setting and the open setting.
In an especially advantageous embodiment of the invention, a provision is that at least one sealing element is arranged between the wall element and an adjacent housing element. This enables a reliable sealing of the gap between the wall element and the adjacent housing element. Such a gap may result particularly with a movement of the wall element between the sealing setting and the open setting. Pressure losses in the flow channel can be especially reliably prevented by the sealing element, which means that the efficiency of the gas turbine is increased independently of the setting of the wall element. The sealing element in this case can be arranged such that the wall element glides along the sealing element when there is movement between the sealing setting and the open setting. Alternatively, the sealing element can also be attached to the movable wall element and glide along on the other housing element.
Other advantages result in that a surface of the wall element adjoining the flow channel and a blade disk of the guide blade are at least essentially connected flush with one another in the sealing setting. The side of the blade disk facing toward the flow channel and the side of the wall element adjoining the flow channel thus form an essentially smooth surface, from an aerodynamic perspective. A particularly low amount of undesirable turbulence is thereby induced in the flow of gas at the transition between the blade disk and the wall element. A small gap in this case can essentially remain between the blade disk and the wall element.
In another advantageous embodiment of the invention, a provision is that the wall element includes an opening, in which the blade disk of the guide blade is arranged. In doing so, preferably a clearance fit is provided between the blade disk and the opening, so that the guide blade and the wall element are movable relatively with respect to one another. Thus, the wall element can serve as a guide for the adjustable guide blade. On the other hand, the guide disk can serve as a guide during adjustment of the wall element between the open and the sealing setting. In another advantageous embodiment of the invention, a provision is that the wall element and the guide blade be fastened to one another with friction contact in the sealing setting.
This means that the wall element exerts such normal force onto the side of the guide blade leaf placed into contact in the sealing setting that a relative movement of the guide blade is prevented, at least under normal operating conditions of an assigned gas turbine. This enables especially reliable, reversible positioning assurance of the guide blade, so that an additional setup to fasten the variably adjustable guide blade can even be advantageously omitted.
In another advantageous embodiment of the invention, a provision is that the housing includes at least one stop element, which limits the movement of the wall element into the sealing setting and/or into the open setting. The stop element or elements represent a constructively simple and operationally reliable option to limit the relative movement of the wall element, particularly swiveling, rotating, and/or bending opposite the adjoining housing elements. Thus, the housing elements adjoining the wall element are also particularly well-protected against damage caused by an unreliable movement of the wall element.
A second aspect of the invention relates to a gas turbine, particularly an aircraft engine, having a housing according to any of the preceding exemplary embodiments. The resulting features and the advantages thereof are contained in the descriptions of the first aspect of the invention, in which advantageous embodiments of the first aspect of the invention can be considered advantageous embodiments of the second aspect of the invention.
A third aspect of the invention relates to a process for operating a gas turbine having a housing according to the first aspect of the invention. In order to enable reliable guide blade adjustment, on one hand, and an improved level of efficiency of the gas turbine, on the other hand, a provision according to the invention is that the wall element be moved between the sealing setting and the open setting. The resulting features and the advantages thereof are contained in the descriptions of the first aspect of the invention, in which advantageous embodiments of the first aspect of the invention can be considered advantageous embodiments of the second aspect of the invention.
In an advantageous embodiment of the process, a provision is that the wall element be moved initially into the open setting. Thereby, the gap between the side of the blade leaf of the adjustable guide blade facing toward the wall element and the wall element is exposed. In a second step, the guide blade is then adjusted. Subsequently, the wall element is then moved back into the closed setting, whereby the flag gap between the wall element and the side of the blade leaf of the adjustable guide blade facing toward the wall element is at least predominantly again closed. Thus, it is particularly possible to move the wall element into the open position and to maintain it there merely so long as is necessary for the desired adjustment of the guide blade. Subsequently, the wall element can be moved directly back into the sealing setting in order to again at least essentially close the flag gap. Thus, throttle losses and therefore also the fuel consumption of the gas turbine can be advantageously minimized.
Additional advantages, features, and details of the invention result from the following description of the preferred exemplary embodiments as well as the drawings.